• Dipankar Mandal

      Articles written in Bulletin of Materials Science

    • Synthesis of Er3+ and Er3+ : Yb3+ doped sol–gel derived silica glass and studies on their optical properties

      Dipankar Mandal H D Banerjee M L N Goswami H N Acharya

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      Er3+ and Er3+ : Yb3+ doped optical quality, crack and bubble free glasses for possible use in making laser material have been prepared successfully through sol–gel route. The thermal and optical, including UV-visible absorption, FTIR etc characterizations were undertaken on the samples. The absorption characteristics of Er3+ doped samples clearly revealed the absorption due to Er3+ ions. On the other hand Yb3+ : Er3+ doped samples showed enhanced absorption due to ${}^{2}F_{7/2} \rightarrow {}^{2}F_{5/2}$ transition. The absorption and emission crosssection for ${}^{2}F_{7/2} \leftrightarrow {}^{2}F_{5/2}$ of Yb3+ were estimated. FTIR absorption spectra have clearly shown the reduction of the absorption peak intensity with heat treatment in the range 3700–2900 cm-1. The 960 cm-1 band also showed progressive decrease in the absorption band peak intensity with heat treatment. The result of the investigations with essential discussions and conclusions have been reported in this paper.

    • Bandgap determination of P(VDF–TrFE) copolymer film by electron energy loss spectroscopy

      Dipankar Mandal K Henkel K Müller D Schmeißer

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      The ferroelectric 𝛽 of poly(vinylidene fluoride trifluoroethylene), P(VDF–TrFE) is confirmed for 100 nm thickness spin coated copolymer film. The homogeneous coverage of the copolymer film is investigated by the help of X-ray photoelectron spectroscopy (XPS). Most importantly, the existing bandgap in the crystalline phase of the copolymer is determined directly from the electron energy loss spectroscopy (EELS).

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